1. Field of the Invention
The present invention relates generally to subsea inspection systems, and more particularly to subsea ultrasonic inspection systems employing electromagnetic acoustic transducers (EMATs) to inspect subsea objects, such as subsea tubular items, conduit, piping, pipelines, risers, vessels, structures, and so forth.
2. Description of the Related Art
This section is intended to introduce the reader to aspects of art that may be related to aspects of the present invention, which are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present invention. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.
Subsea piping and vessels, and other subsea structures, may be involved in the recovery and transmission of energy resources, such as oil and gas. In a more general and broader sense, such subsea piping and structures may be found in a range of commercial and industrial applications, including utility distribution, manufacturing processes, chemical and petrochemical transport, energy transmission, plumbing, heating and cooling, as well as in the recovery of spent chemicals/compounds, and so forth. In operation, subsea piping, vessels, and structures may serve to collect, distribute, and transport water, steam, chemicals, petrochemicals, crude oil, natural gas, and other liquids, gases, and components. Subsea piping and vessels, and other subsea structures, have played a beneficial role in improving productivity in delivery of resources, including applications in the recovery of offshore oil and gas. Indeed, world economies depend on the capability of subsea pipelines and structures to transport feedstocks and products to a diverse range of customers and end-users. Construction of subsea pipelines and structures has occurred over the last several decades, including many such relatively old subsea pipelines and structures still in use and in service.
Subsea piping, pipeline, vessel, and structural failures may be caused by mechanical harms, corrosion, erosion, damaged coatings, adverse operating condition, sea currents, and generally the relatively harsh subsea environment. In regard to corrosion, the external surface of the subsea object is generally exposed to potentially corrosive seawater, and the internal surface of the object (e.g., subsea piping and vessels) may be exposed to corrosive contents. Moreover, internal erosion may occur due to the flow of the contents through the subsea piping, pipeline, or vessels. Such erosion may be exacerbated by centrifugal forces associated with changes in the direction of the flow path. Significantly, erosion, corrosion, and other damage may cause gouges, cracks, stress corrosion cracking, and reduce the wall thickness of the subsea pipe or vessel, and thus reduce the pressure rating or pressure-holding capacity of the subsea pipe, pipeline, or vessel, as well as make subsea objects more susceptible to failure. Accordingly, operations and maintenance personnel of subsea objects (e.g., subsea piping, pipelines, vessels, risers, structures, etc.) may provide for inspection of the subsea objects, including in-place or in situ inspection and at a regular frequency. Such inspections of mechanical integrity may be related to or governed by applicable government or industry standards.
The inspection of subsea objects may involve visual inspection by a diver or inspection via hand-held devices by a diver, for example. However, the use of divers for subsea inspection may be problematic where the subsea objects are relatively deep and/or where and when strong sea currents exist. With regard to subsea pipelines, various techniques have been employed to detect defects, corrosion, and cracks in the pipelines. For example, pipeline inspection gauges or “pigs” may be pumped or pressured through the subsea pipeline to detect corrosion or cracks in the pipeline, and to measure thickness of the pipe wall. An intelligent or smart “pig” may include electronics and sensors that collect various forms of data during the trip through the pipeline. Modern intelligent pigs may be highly sophisticated instruments that vary in technology and complexity by the intended use and by manufacturer. However, valves and other components along the pipeline may give internal obstructions in the pipeline making use of a pig problematic.